an undisturbed sediment core containing varves from the deposition zone of a deep lake the varves...
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An undisturbed sediment core containing varves from the deposition zone of a deep lake
The varves can be used to calculate dates along the core profile
Paleolimnology--Pollen stratigraphy in lake sediment cores
Cores can be dated with radioisotopes
137Cs (half-life 30 yr) is found in fallout from bomb tests
The most commonly used isotope is 210Pb, half-life 22 yr
210Pb
218Po
222Rn
226Ra
238U
The Uranium 238 decay series
The littoral zone, what determines its outer boundary?
The transparency of lake water is measured by its extinction coeficient
The extinction coefficient k increases with:
•the concentration of organic matter (colour) of the water
•the amount of suspended mattereg, phytoplankton, fine suspended particles, eg
clay
Light extinction --Light enters from above and its intensity (I) is sharply attenuated with depth (z)—absorption by water or solute molecules or scattered by particles
Iz
z
Photiczone
z 50%
z 1%
z 10%
Section 10.6
Page 144 in text
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In general Photosynthesis exceeds respiration above the 1% light level and rooted plants can grow down to about the 10% light level
Iz
z
Photiczone
z 50%
z 1%
z 10%
Page 144 in text
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